A board-on-chip (BoC) is a semiconductor integrated circuit (IC) device where the die and the circuit board are attached and encapsulated as one package. The die and board are typically attached, prior to encapsulation, by double sided adhesive tape applied to the bottom of the board and top of the die. The die is also electrically connected to the board by bond wires. The then attached die and board are completely encapsulated (packaged) for protection with a compound, such as plastic. The compound is injected into a mold and onto the die and board at a high pressure in a hot molten liquid form. The compound then cools and hardens to form a protective package.
The encapsulation process is complex because a desired exterior surface of the board, containing the ball grid arrays (BGA), must only be partially sealed with the compound used for encapsulation. In particular, the bond wires on the exterior surface of the board must be sealed with the encapsulating compound but the compound cannot contact the ball grid arrays. If the compound contacts the balls of a ball grid array the device will be damaged because the connectivity of the board to external circuits will be negatively impacted.
In a conventional BoC package, the board is physically attached to the die by two pieces of double sided adhesive tape, placed in between the die and board. The die is electrically connected to the board by bond wires which pass through a bond wire slot in board. The bond wires are all physically located between the two pieces of adhesive tape, in the bond wire slot.
During encapsulation the compound must fill the bond wire slot and cover all bond wires on the board, but the compound must not flow beyond the edges of the ball grid arrays. The molding compound is introduced into the BoC package under high pressure at a mold gate. The molding compound then begins to fill a mold containing the die and encapsulates the BoC package. In this conventional BoC package the bond wire slot may fill before the molding compound has completely encapsulated the entire die. Thus, the compound may begin to flow up and over the top of the board and past the edges of the ball grid arrays, before the die is encapsulated. As described above, when the molding compound contacts the ball grid arrays, the BoC package may be damaged.
The foregoing problems of encapsulation of a BoC package are undesirable aspects of conventional semiconductor packaging techniques. A system and method are needed to better encapsulate a BoC package such that the ball grid array will not be damaged during encapsulation.
Thus, a need still remains for method of manufacturing that will yield reliable and easy to assemble BoC package. In view of the ever increasing demand for very small and functionally complicated electronic devices, it is increasingly critical that answers be found to these problems. In view of the need to save costs and improve efficiencies, it is more and more critical that answers be found to these problems. Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.